Large numbers of the files being managed by companies and so forth are either complete or partial matches to other files. For example, when a file has been backed up numerous times, large numbers of the same file are created. In addition, in a case where a portion of an existing file is updated to create a new file, many parts of the new file will be identical to the existing file. The generation of large numbers of duplicate files like this wastefully consumes a storage resource.
Accordingly, technology for detecting and eliminating duplicate files has been proposed. The prior art detects duplicate data by partitioning a file into variable lengths and computing a hash value for each partitioned piece of data (Patent Literature 1).
In this prior art, a hash value is computed for each prescribed size from the start of a file, and a determination is made as to whether or not this hash value matches with a predetermined constant value. When the hash value matches the constant value, the file is partitioned at this part.